Polyglycerol (or otherwise hereinafter referred to as “polyglyceride”) monoethers such as polyglycerol monoalkyl ethers have been produced according to various processes utilizing for example chlorohydrin or a chlorohydrin-based reactant. In some cases, glycerol ethers can be prepared from glycidol, epichlorohydrin or a glycidol ether treatment with an alcohol or phenol and catalyzed by an acid or alkali.
As one example, a process can include adding epichlorohydrin to an alcohol under basic conditions. Dehydrochlorination and ring-closing are carried out under these basic conditions, and ring-opening is carried out with a diluted sulfuric acid. This procedure is repeated until a target degree of polymerization is obtained. This process of making polyglycerol monoethers, however, is not desirable if the polyglycerol monoethers are to be utilized in cosmetics, food, detergents or the like, because the finished product may contain undesired chlorine compounds. There are also concerns about the safety of chlorohydrin or a chlorohydrin-based compounds as, for example, the use of epichlorohydrin is unsafe and is classified under CMR (Carcinogenic, Mutagenic or Toxic to Reproduction).
In addition, in order to produce a product having a high degree of polymerization, use of the above-referenced process can involve complicated reaction steps and a high relative cost. The reason is because a product having a single degree of polymerization alone is obtained according to the process described-above.
As another example, a process can include adding glycidol to a compound having a phenolic hydroxyl group, such as an alkylphenol, which has a high reactivity associated with the phenolic hydroxyl group. Similar to epichlorohydrin the use of glycidol is unsafe and requires special precautions in handling and transportation. Moreover, glycidol is reasonably anticipated to be a human carcinogen and, as such, it is not suitable and/or desirable to use in home and personal care applications, cosmetics, foodstuffs, detergents, cleaners, etc. and the like.
Yet another process includes reacting an aliphatic alcohol with a glycidyl ester, such as glycidyl acetate, in the presence of an alkali metal catalyst. Yes another process includes reacting an organic hydroxyl compound with benzyl glycidyl ether in the presence of a phase-transfer catalyst. Such processes, however, carry out protection and deprotection of glycidol and are thereby complicated in procedures, although target compounds are obtained. In addition, these processes are not chemically and industrially safe when an acid hydride, for example, is used as a protecting reagent, because an acid formed in the system may invite an abnormal reaction.
Polyglycerol monoethers are known substances but have not been generally used, because they contain large amounts of impurities such as polyglycerols, dialkyl components, residual amounts of epoxide containing compounds such as glycidol, chlorohydrin, dichlorohydrin and related compounds, which may be human carcinogens and/or classified under CMR, and are also costly to produce.
Analogous compounds such as polyglycerol mono(fatty acid) esters and polyoxyethylene monoalkyl ethers have been used in cosmetics, home and personal care applications, detergents, etc. However, use of polyglycerol fatty acid esters, for example, are limited because of its insufficient in resistance to hydrolysis, to salts, and to acids. Polyoxyethylene monoalkyl ethers may yield formaldehyde and are low in water-solubility. Such formaldehyde has been perceived as a problem. Accordingly, demands of the market have been made on replacements of these compounds.
Accordingly, there is a need for an improved process for making polyglycerol alkyl ethers without the drawbacks as mentioned above.